The present invention relates to an optical amplifier device for an optical transmission system and, more particularly, to an optical amplifier device for an optical transmission system with bidirectional wavelength multiplex to a light transmission waveguide.
An optical amplifier device is known for an optical transmission system with bidirectional wavelength multiplex to a transmission wave guide. The known optical amplifier device includes a first optical amplifier for amplifying signals of a first wavelength in a first direction; a second optical amplifier for amplifying signals of a second wavelength in a second direction; a first wavelength selective coupler connecting the input of the first optical amplifier and the output of the second optical amplifier with the light transmission wave guide and a second wavelength selective coupler connecting the input of the second optical amplifier and the output of the first optical amplifier with the light transmission wave guide.
An optical amplifier device of the above-described kind is described in European Published Patent Application EP 445 364 A2. An optical transmission system with wavelength multiplex is described in this reference in which a wavelength selective coupler is arranged upstream and downstream of an optical amplifier and the second light guide inputs of the couplers are connected with each other by an optical amplifier. The first optical amplifier amplifies signals of a first wavelength and the second optical amplifier amplifies signals of a second wavelength. To prevent noise in the amplification path due to multiple reflections which cause a deterioration of the signal-to-noise ratio due to the retarded useful signal components, low reflecting wavelength selective couplers are of particularly great significance.